Friday afternoon: Car started with difficulty
Saturday morning: Battery was dead. Started car with charger. Drove about 25 miles and stopped car for gas. Car restarted fine. Drove another 25 miles. Car sat for about 7 hours. Restarted fine. Drove car about 50 miles and parked for the night at about 7pm. Noticed voltage on dash display dropped to low 12 volt range. Conclusion is alternator and battery were working well enough to get some charge on the battery.
Sunday afternoon: Battery was dead. Started car with charger. Conclusion was battery couldn’t hold charge. Drove car about 30 miles to O’Reilly Auto Parts. Tech checked charging system. Said alternator was fine but battery was bad. Replaced battery. Still noticed voltage dropping from mid 13 range to mid 12 range while driving home. Put charger on battery overnight.
Monday morning: Car started fine with voltage in mid 13 range. However voltage again dropped to mid to low 12 after starting to drive. Drove about 80 miles. Noticed voltage would increase to mid 13 to 14 range when decelerating. However, once I stepped on the gas the voltage dropped back to the low to mid 12 range. Took the car to a service garage. Tech checked system and said the alternator was malfunctioning. Put battery on charger for the night.
Tuesday morning: Drove 40 miles to another service garage for second opinion. Told them about the voltage increasing while decelerating and dropping when gas was applied. They couldn’t duplicate but they didn’t take it on the road. They said alternator was bad.
Tuesday afternoon: While in my garage I checked voltage of battery. It was 12.6. I started the engine and the voltage jumped to 14 on both the meter and the dash display, but in a relatively short time dropped to around 12.6 on the meter and 12.4 on the dash display. When I revved the engine the meter would increase to about 13, but the dash display remained at 12.4. Decelerating while not moving, the voltage on the dash display did not increase like it does on the road. Conclusion is alternator works to some degree or else voltage wouldn’t increase with increased engine rpm’s, but there is no explanation for dropping and rising voltages on the dash display or why the meter showed voltage increase to 13 when the engine was revved but the dash display stayed at 12.4.
Is there something other than the alternator that would cause this behavior?
Your vehicle is equipped with a Generator Current Sensor. I have also seen this part refereed to as a battery control module. It is possible that this component is failing and or the alternator. However both are controlled by the PCM. I have added the charging system wiring diagram below for reference.
What is a generator current sensor?
The generator current sensor is a Hall-effect sensor attached to the generator B+ cable. … The PCM reads the generator current sensor feedback voltage to determine how much current is flowing through the generator B+ cable.
How do I know if my battery sensor is bad?
The battery sensor helps the system continuously adjust the system voltage, and if it fails, this process may be disturbed. An incorrect or inconsistent signal from the battery temperature sensor may cause the system voltage to fluctuate, which will cause the engine to surge
